CVE-2026-98344dmaengine: Fix device kref underflow in dma_chan_put()

Official description

In the Linux kernel, the following vulnerability has been resolved: dmaengine: Fix device kref underflow in dma_chan_put() dma_chan_get() takes chan->device->ref only on the slow path: /* no kref on fast path */ if (chan->client_count) { __module_get(owner); chan->client_count++; return 0; } if (!try_module_get(owner)) return -ENODEV; if (!dma_device_get(chan->device)) { // calls kref_get_unless_zero() dma_chan_put() drops the ref unconditionally, so every fast-path get/put pair drops one extra device reference. The bug fires when two conditions hold together: a non-private provider has a persistent client holding chan->client_count > 0 and another client cycles dmaengine_get()/dmaengine_put(). When the kref hits zero, the subsequent dma_find_channel() returns NULL even though the provider module is still loaded. Fix this by dropping device->ref only on the last put, matching the single slow-path get.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/036b527f92570206da4b8c40b38f8d689e29d0f3
• https://git.kernel.org/stable/c/5fb1797a8c9485e40e5492fa0338ab5c7d1f3fef
• https://git.kernel.org/stable/c/57f7f1c6827be7d8f80feca48d2125fb91c6f6ed
• https://git.kernel.org/stable/c/7c3f4ce651d43705f9ec7f778f642a90d5ff4fba
• https://git.kernel.org/stable/c/de2677e57d3161390d8a508f08cddec6ef7e4b23
• https://git.kernel.org/stable/c/1a0d9b406febf23054ad595fd47b29325e70fb2d
• https://git.kernel.org/stable/c/77906ac448d2fa81fa710ae26c0e591ebdc81154
• https://git.kernel.org/stable/c/44dab659064eb5c10adb0306510eebe848ed592d